The power supply circuit of a computer system provides usable power to the electrical components and devices of the computer. Because most computers require voltage and current different from that generated and supplied by local utility companies, the computer's power supply must convert the incoming voltage and current to a form appropriate for use by the computer. For example, most utility companies in the United States produce power at 120 volts, as 60 hertz, sinusoidal alternating current (AC). A computer system, however, typically requires direct current (DC) power at a voltage level significantly lower than 120 volts, such as 12 volts or less. Hence, the computer's power supply converts "utility power" into "computer power."
As computer technology has progressed, computers have become more "powerful" and, as a consequence, require more electrical power, and are therefore more costly to operate than earlier computers. The impact of increasing operating costs of computers is particularly acute in large organizations having networks comprising a large number of computers. It is therefore desirable that computers be operated efficiently and economically so that operating costs are minimized. To this end, some computers are provided with power supplies having support circuitry that measures power consumed on the primary side of a power supply transformer and reports the measurements as a serial bit stream of data to a computer microprocessor on the secondary side of the transformer. Such support circuitry, however, comprises a relatively expensive microcontroller and, as a consequence, is relatively expensive to implement. It can be appreciated that the savings in operating costs made possible by such support circuitry are, to a certain extent, offset by the cost of the microcontroller required to achieve the savings, thereby defeating the purpose of the microcontroller.
Therefore, what is needed is a low cost (i.e., a non-microcontroller) system for measuring the amount of power, or energy, consumed by a computer on the primary side of the PC transformer and for generating to the secondary side thereof data indicative of the power measured.